Raman spectroscopy is a method in which light of a mono-wavelength is projected onto a material and the obtained scattered light is spectroscopically (in a spectroscopic fashion) divided to obtain the Raman spectrum of Raman scattered light and is employed for, for instance, identification of the material. Since the Raman scattered light is weak, there has been developed surface enhancing Raman device where the Raman scattering is enhanced on the surface. As one of the surface enhancing Raman devices, a device using a local plasmon resonance can be shown. This device is based on the fact that when light is projected onto a metal body, especially a metal body having an irregularity of an order of nanometer, in a state where the material is in contact with the metal body, an electric field is enhanced by a local plasmon resonance and the intensity of the Raman scattered light of the sample in contact with the metal body is enhanced. It is said as the regularity of the fine structure of the metal body is higher, an electric field enhancement which is more uniform and more effective can be obtained.
As one of methods of producing a fine irregularity structure on the surface of metal body, a method where metal particles highly uniform in particle diameters are prepared and the metal particles is randomly fixed to the surface of the metal body can be shown. In Japanese Unexamined Patent Publication No. 2003-49205, there is disclosed a method of producing metal particles highly uniform in particle diameters where an organic ligand having a hydrophobic group is coordinated around metal particles, and the metal particles are solidified as the ligand is coordinated. By such a method, metal particles which are highly uniform in particle diameters and small in aggregation of the particles can be obtained.
In Japanese Unexamined Patent Publication No. 2005-172569, there are disclosed a fine structure where metal particles of an order of nanometer are positioned in regularly distributed fine holes and a Raman spectroscopic device using the fine structure.
However, the method disclosed in Japanese Unexamined Patent Publication No. 2003-49205 requires the steps of coordinating the organic ligand with the metal, solidifying the same and removing the solvent used in the step of coordinating the organic ligand with the metal and number of steps are required before fixing the fine particles to the metal body. Further, in Japanese Unexamined Patent Publication No. 2003-49205, there is not disclosed a method of regularly fixing the fine particles uniform in particle diameters to the metal body.
In a fine structure disclosed in Japanese Unexamined Patent Publication No. 2005-172569, the problem described above is overcome and a highly regular fine structure can be produced. However, in order to obtain more effective surface enhancement in the surface enhancing Raman devices, it is necessary to conform the measuring light with the resonant wavelength at which the surface enhancing Raman effect can be obtained (the wavelength will be simply referred to as “the Raman effect enhancing wavelength”, hereinbelow), and in the Raman spectroscopy which requires a change of the wavelength of the measuring light according to the object material to be detected, the surface enhancing Raman devices having a Raman effect enhancing wavelength according to the wavelength of the measuring light becomes necessary. In the surface enhancing Raman devices using local plasmon resonance, a complicated design change of carrying out a precise control of the metal fine structure at each wavelength becomes necessary in order to conform the wavelength of the measuring light to the local plasmon resonant wavelength.